Slider
FREEAdjustable slider with bidirectional feedback
When to reach for it
Slider commands a single continuous value over a topic: motor PWM, servo angle, gripper width, a velocity setpoint. Turn on Track Robot State (Pro) for a feedback ghost as the robot converges on the command. Reach for Knob when the control should feel like a rotary dial, or Joint Sliders (Pro) for more than one joint at once.
Worked example: gripper width
A parallel gripper with an 85 mm stroke, driven by a node expecting a position setpoint. Topic /gripper_width_cmd, schema std_msgs/msg/Float64. Min 0.0, Max 0.085, Step 0.001. Turn on Publish on Release Only: a gripper needs one final width, not the whole drag. Leave it off, the factory default, for a live setpoint like a target velocity.
Watch out for
- Min Value, Max Value, and Step are the scale the app enforces, not a safety limit. The robot does whatever value you send, so match them to the receiver.
- The outbound message is always shaped
{ "data": <value> }, whatever Message Type says. It fitsstd_msgs/msg/Float64orFloat32; a schema needing the value under a different key never gets it. - On Pro, if Track Robot State is on and feedback never settles within Recouple Timeout (ms), the thumb auto-jumps to feedback rather than stay stranded. A teleporting thumb means the controller stalled, not a broken widget.
Configuration fields
The topic this widget publishes to. While connected, tap to pick one the robot advertises.
The ROS message type, like sensor_msgs/msg/Image. Fills in when you pick a topic.
Send one value on release instead of streaming while you drag.
How fast the slider streams updates when the user is dragging.
WITH PRODefault 10 Hz. Raise to 20 to 50 Hz for smoother sweeps, lower on slow links. No effect with Publish on Release.
Show the robot's actual value as a ghost indicator alongside your command.
WITH PROSee the robot's actual value as a ghost next to your command, live as it moves.
Topic carrying the robot's actual value, drawn as a ghost alongside your command.
Field path on the feedback topic to read as the actual value.
Messages per second this widget takes from the feedback topic. Lower saves data, higher tracks closer.
0.1 to 60, step 0.1How long the thumb holds your value after release while feedback settles. Raise it for slow controllers.
500 to 10000, step 500Ease the ghost and thumb toward the robot's reported value instead of snapping to every sample.
WITH PROCalms jumpy or noisy feedback on screen. Your commanded value is unaffected.
How strongly to smooth the feedback. Heavy damps a noisy controller but adds lag.
Show a name on the widget.